Different types of joint mechanisms for glasses frames are known. The most common type is based on a hinge mechanism in which pins are disposed on the frame or respectively the rim of the lenses, which cooperate with a respective hinge disposed at the end on the side of the temple which is on the side of the rim by interleaving both parts and by connecting them by means of special screws such that they are pivotable. In most glasses rims, in particular in those which are used with corrective glasses, opening and closing the rims for inserting or for changing the lenses is carried out by means of a so-called closing block. The lenses can also be directly attached to a frame by screwing screws directly into the lens. In glasses without a frame, the temples are directly screwed with the lenses by means of a projecting part.
Since the swivel joint is subject to high dynamic loads during lifetime of the glasses, in several solutions, no traditional swivel joint is used for reasons of simplification.
Thus, the U.S. Pat. No. 3,155,982 proposes glasses in which the temples directly cooperate with the front part of the rim which contains the lenses. Therefore, the end of the temple which is on the side of the rim is divided into three leaf springs, wherein the central leaf spring abuts on the external edge of the rim part, whereas the two external leaf springs engage with openings disposed near the external edge in the central piece by means of hooks formed at their ends. A disadvantage of the joint mechanism described in U.S. Pat. No. 3,155,982 is the fact that the glasses temples are only attached to the rim very loosely such that the glasses temples can be loosened from the holder very easily, e. g. when the glasses fall on the floor.
Another solution for a glasses joint which as well uses a glasses temple which is provided with three leaf springs is proposed in the European Patent No. 0 863 424 B1 of Haffmans and Gottschling. On the rim, respectively one connecting element is provided on the left and on the right, which has an upper and a lower recess which forms a joint axis which is perpendicular to the direction of the temple in its folded-up state. In the folded-up state of the temples, the two external leaf springs of the temples engage with the recesses in the connecting element from the surface of the connecting element which is faced to the face of the wearer of the glasses by means of curved shapes which are provided on their free ends and then abut on the surface of the connecting element which is not faced to the face of the wearer of the glasses, whereas the central leaf spring abuts with its entire length on the opposite surface of the connecting element. The connecting element therein is divided in two pieces; thus, it is easily possible to change the lenses. For stabilization, a closing clip can be used which can be pushed over the two-piece connecting element. This mechanism however has the disadvantage that inserting the temples is difficult since the external leaf springs and the central leaf spring have to be guided on opposite surfaces of the connecting element, wherein this operation has to be effected by moving against the resilience and the curved shapes of the ends are disturbing. Furthermore, in particular if the dimensions of this joint are very small, there is a risk that the temples are detached from the connecting element even in the case of low mechanical load.
From the French publication FR 2 779 241, a glasses frame having a glasses joint is known which is achieved by providing with pins the end of the temple on the side of the rim, which engage with recesses of a connecting element on the rim, wherein clips of the connecting element overlap the end on the side of the rim when the temple is swivelled. Such a joint however does not assure a safe holding of the temple in the case of excessive mechanical load.
A joint mechanism is described in WO 98/148313 in which two fingers, one mounted on each of the joint-side ends of the glasses temple, are arched away from one another and the curved ends engage rotatably in apertures which are arranged on a connecting element on the frame side. The curved ends of the fingers are held secure in these apertures in that these fingers exert a certain spring resilience upward and downward. Such a joint mechanism, however, is not associated with flat metal glasses like those for instance in EP 0 863 424 B1.